High-frequency drying apparatus

ABSTRACT

An improved apparatus for the high-frequency drying of strip or thread shaped fibrous material in a continuous process. The highfrequency drying field is produced between adjacent opposite polarity elongated electrodes disposed in the peripheral surface of a rotatably mounted electrode structure or arrangement in the shape of a truncated cylinder. At least one of the side or end plates of the cylinder is provided with an opening to provide the intake of a ventilation channel, which includes the interior of the cylinder between the two side plates and whose outlet passes through the space between adjacent electrodes. The power tube for the high-frequency generator is disposed in the ventilation channel at least partially in the axial space between the two side plates.

[451 July 18, 1972 [54] HIGH-FREQUENCY DRYING APPARATUS [72] Inventor: Herbert Hanfl, Berlin, Germany [73] Assignee: Llcentla Patent-Verwaltungs-G.m.b.ll.,

Frankfurt, Germany [22] Filed: Aug. 26, 1970 [2|] Appl.No.: 67,139

FOREIGN PATENTS OR APPLICATIONS 952,104 3/1964 Great Britain ..2l9/l0.61

Primary ExaminerCarroll B. Dority, Jr. Attorney-Spencer & Kaye 57 ABSTRACT An improved apparatus for the high-frequency drying of strip or thread shaped fibrous material in a continuous process. The high-frequency drying field is produced between adjacent opposite polarity elongated electrodes disposed in the peripheral surface of a rotatably mounted electrode structure or arrangement in the shape of a truncated cylinder. At least one of the side or end plates of the cylinder is provided with an opening to provide the intake of a ventilation channel, which includes the interior of the cylinder between the two side plates and whose outlet passes through the space between adjacent elec trodes. The power tube for the high-frequency generator is disposed in the ventilation channel at least partially in the axial space between the two side plates.

8 Claims, 3 Drawing figures Patented July 18, 1972 3,676,936

2 Sheets-Sheet 1 Fig.

, lnvpmarr Herbert Hcnff ATTO Patented July 18, 1972 3,676,936

2 Sheets-Sheet mama/.- Herbert Honff ATTORNEYS HIGH-FREQUENCY DRYING APPARATUS BACKGROUND OF THE INVENTION The present invention relates to an improved apparatus for high-frequency drying of strip or thread shaped fibrous material in a continuous process. For example, the present invention may be applied in the fabrication of paper or in the manufacture of threads of natural or synthetic fibers.

In such high-frequency drying apparatus, it is necessary to keep the electrode arrangement utilized to create the highfrequency field as clean and dry as possible during operation. This necessity arises in order that the apparatus be able to stay within the load limits determined therefor with a dry and clean electrode arrangement and with the voltage load applied thereto during operation, and particularly after a long period of operation, without requiring any additional maintenance work.

According to a previous proposal for a device for highfrequency drying of strip or thread shaped fibrous materials in a continuous process, a rotatably mounted electrode arrangement having the outline of a truncated cylinder, i.e., one whose height is small relative to its diameter, is provided. The individual electrodes are disposed in the outer surface of the cylinder with electrodes of opposite polarity being adjacent one another about the periphery of the cylinder. An opening is provided in the center or substantially in the center of one of the side plates of the electrode arrangement, which opening serves as the intake for a ventilation channel which includes the space between the side plates, and whose outlet passes through the outer surfaces of the cylindrical electrode arrangement in all areas between adjacent electrodes. (c.f., German Pat. application P 65 887.4)

SUMNIARY OF THE INVENTION While the above mentioned electrode arrangement operates satisfactorily, it still presents some shortcomings with respect to dryness of the electrodes and efiiciency of the entire device.

The present invention provides a primary improvement of this older proposal in that the air penetrating the interstices between adjacent electrodes is preheated without requiring any additional expenditures. The improvement is obtained in that according to the present invention a power tube of the high-frequency generator feeding the apparatus is disposed in the ventilating channel and at least partially in the portion thereof disposed between the outer surfaces of the side plates.

This arrangement according to the present invention has the advantage that the air flowing through the ventilating channel can thus be utilized both to cool the power tube, and after being heated by the heat given oil" by the power tube, to heat the entire structure of the rotating electrode arrangement and thereby prevent precipitation of moisture on the electrode components.

Additionally, by installing the tube in the interior of the rotating electrode arrangement, the connecting lines or conductors in the generator structure are shortened in a desired manner so that a high operating frequency can be obtained to produce the best possible high-frequency energy absorption in the strip or thread of material. The installation of the power tube in the interior of the cylindrical electrode arrangement and preferably coaxial therewith also provides the further advantage that it avoids high-frequency power losses which would otherwise inevitably be produced by high-frequency power lines with one or two-cycle high-frequency generators. Moreover, such a positioning of the power tube results in a reduction in space requirements, which is of particular importance in the spatial limitation of industrially employed devices. The power tube is thus also easily accessible and can be rapidly replaced without difficulties.

A particularly good adaptation to the thus produced favorable cooling conditions for the power tube results when the power tube is provided with an external anode designed for air cooling. In a preferred embodiment of the apparatus according to the present invention, the electrode terminals of the power tube are constituted by coaxially disposed cylindrical ring elements. These electrode terminals are advantageously disposed to be coaxial with the peripheral outline of the area enclosing the electrode arrangement between the side plates of the electrode arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of an embodiment of the present invention.

FIG. 2 is a schematic sectional view of the embodiment of the invention of FIG. 1 taken along the line 2-2 of FIG. 1.

FIG. 3 is a circuit diagram illustrating the operation of the power tube together with the impedance elements provided by the device of FIG. 1 which form the high-frequency generator.

DESCRIPTION OF THE PREFERRED EMBODINIENTS Referring now to FIGS. I and 2 there is shown a housing wall I provided with a bearing tube 2 which is fastened to the housing wall 1 by means of a fastening flange 9. Rotatably mounted on the bearing tube 2 by means of a ball bearing 26 is a bearing ring 3 which supports a circular side plate 5 of the electrode arrangement. Fastened to the inner surface of the side plate 5 is an insulating plate 6 which, via the ventilating wings l3 mechanically supports a correspondingly arranged insulating plate 6 on the other side of the electrode arrangement. The latter insulating place 6' is fastened to a circular side plate 7 on the other side of the electrode arrangement. The side and end plates 5 and 7 bear the rod electrodes 12 and II respectively which engaged in one another in a comblike manner, thus forming a rotatable electrode arrangement in the shape of a truncated cylinder.

The housing wall 1, the side wall 5 and preferably the side wall 7 are each provided with an opening in substantially the center thereof so as to form the intake for a ventilation channel through which air will be circulated. The air entering the ventilation channel via the opening in the wall I flows through the axial chamber formed by the side plates 5 and 7 and then through the space between the side plates and exits from the cylindrical electrode arrangement via the spaces between the electrodes 11 and 12.

According to the invention, as illustrated, the power tube 18 for the high-frequency generator feeding the electrode arrangement is mounted within the intake for the ventilation chamber. Preferably, as illustrated, the power tube I8 is mounted along the axis of the intake chamber of the ventilation chamber and extends beyond the respective outer surfaces of the side plates 5 and 7. Due to its position in the ventilation chamber, the power tube 18 will be cooled by the stream of cool air entering the ventilation chamber, and the heat removed by this air stream will then heat the remainder of the electrode structure and in particular the electrodes II and 12.

To aid the cooling of the power tube 18 the tube is preferably provided with an external anode and cooling fins 35. Moreover, the tube 18 is preferably constructed so that its electrode terminals 19,20,21 and 22, as illustrated, are in the form of coaxially disposed cylindrical ring-like elements which easily engage the respective contacts 3,28,27,29. Additionally the respective diameters of the ring-like electrode terminals successively increase along the axis of the tube to provide for ease in replacing the tube. As can be seen in the illustration in FIG. 1 the power tube 18 can easily be removed from its seat in a direction toward the right and can be replaced by a new tube.

The side plate 5, due to its short distance from the fastening flange 9, has a high capacitance with respect to the housing wall I, whereas the side plate 7 has the corresponding capacitance with respect to a coupling plate 8 which is con nected to the grid connection 21 of the power tube 18 via contacts 27. A coupling plate 4 connected to the cathode connection 20 of the tube 18 via contacts 28 has a corresponding capacitance with respect to the coupling plate 8 for the grid connection. The rod electrodes 11 and 12 which are electrically and mechanically connected with the side plates 5 and 7 are fed with a high-frequency voltage from the generator arrangement via the coupling capacitances to the fastening flange 9 on the one side and to the coupling plate 8 on the other side, so that a high-frequency current flows through the operating capacitance between the rows of rod electrodes 11 and 12. Thus, an electric high-frequency field results between the electrodes I1 and 12, which have alternating polarity, and the material to be treated is subjected to a heating and drying process in this high-frequency field.

To support the coupling plates 4 and 8 as well as the connected electrode leads 27 and 28 for the respective cathode terminal 20 and the grid terminal 21 feedthrough terminals or insulators l4 and 15 are provided. The insulators l4 and 15 are permanently mounted at one end in the housing wall I and bear the above-mentioned coupling plates 8 and 4 and contacts 27 and 28 respectively at their other ends. A total of three such feedthrough insulators are provided which serve as mechanical mounts and as inductances in the generator circuit. That is, in addition to the two insulators l4 and 15 which are shown in section in FIG. I, a third insulator 38 (FIG. 2) is provided through which passes the input lead for the contact 23 for the heating filament connection 19 of the tube 18. The feedthrough leads of insulators l4, l5 and 38 are extended toward the outside as the center conductor of coaxial lines I7, 16 and 39 respectively, the outer conductors 30,30'30" of which are connected to the housing wall I. The material to be dried is a thread 34.

The total arrangement is covered on the outside by a housing cover fastened to the wall I by a hinge 31. The housing cover 10 is provided with ducts 32 adjacent the electrodes II and 12 for the removal of the cooling air pressed or sucked into the ventilating channel via the central opening in the wall I. In order to prevent the high anode voltage and the heating filament voltage from being applied to the power tube 18 when the cover 10 is open, the housing is provided with a contact box 24 containing normally open switches for connecting these voltages to the tube l8. These switches are closed by a switching pin 33 mounted on the cover 10 only when the housing cover is closed. Thus when the housing cover 10 is open, these voltages are automatically cut off.

The circuit diagram of FIG. 3 serves to explain how the power tube 18 together with the natural impedances determined by the structure of the device according to FIG. 1 forms a generator circuit which, due to the elimination of longer feeder lines, can be designed to have very low losses and is suited for very high frequencies due to the reduced capacitances and inductances. In FIG. 3 the same reference numerals are used as in FIG. I for corresponding parts. This applies to the rod electrodes 11 and 12 which mesh in the comb-like manner and which are fastened to the conductive side plates 5 and 7. Between housing 1 and side plate 5 as well as between side plate 7 and coupling plates 8 and 4, the abovementioned capacitances become efiective. The coupling plate 4 is connected to the cathode terminal and coupling plate 8 is connected to the grid terminal of tube 18. For reasons of simplicity in the illustration, the cathode of the tube in FIG. 3 is connected directly with the housing and with ground, whereas the anode has the full direct and high-frequency voltage above ground. The terminal Va serves to supply the direct anode voltage Va, and conducts the anode current directly to the tube anode via a high-frequency choice. The feedthrough insulators 14, I5 and 38 of FIG. 1 are indicated in FIG. 3 by identically marked inductances and act as inductances in the diagram in FIG. 3. Thus the inductance 14 of the corresponding feedthrough insulator of FIG. 1 is disposed between the grid and the grid leak resistance 25, whose other end is connected with the housing 1. The feedthrough leads of insulators and 38 are shown as inductances between the respective cathode and heating filament terminals and the corresponding terminals V, to which the heating voltage is applied.

It can be seen that in FIG. 3, tube 18 together with the capacitance and inductance elemens form a three-point voltage divider circuit between the cathode, the grid and the anode, which circuit is suitable for producing high-frequency oscillations and in which the natural capacitances and inductanoes given by the construction of FIG. 1 become effective within the frequency-determining portions of the voltage divider circuit. Since longer leads are furthermore eliminated because of the compact construction, the circuit is suited for the production of oscillations having very high frequencies with high energy output and low losses.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

Especially there may be provided much more electrodes so that the distances between adjacent electrodes may be smaller than shown in the drawings.

I claim:

I. An apparatus for high-frequency drying of strip or thread shaped fibrous materials in a continuous process including, in combination: an electrode arrangement having the outline of a cylinder, means for mounting said electrode arrangement for rotation about the axis of said cylinder, said cylinder having a pair of end plates and plurality of rod-shaped electrodes connected to said end plates and disposed in the peripheral surface of said cylinder, said rod shaped electrodes extending in the axial direction of said cylinder and being arranged so that electrodes of opposite polarity are adjacent one another about the periphery of said cylinder, at least one of said end plates of said electrode arrangement being provided with an opening substantially in the center thereof which constitutes the intake of a forced air ventilation channel which includes the space between said end plates and whose outlet passes through the outer surface of said cylinder in all areas between adjacent ones of said electrodes, a power tube of a high-frequency generator which feeds power to said apparatus to produce the high frequency field between adjacent ones of said electrodes, said power tube being disposed in the intake of said ventilation channel and at least partially in the portion thereof disposed between said end plates, whereby the air flowing through said ventilation channel can simultaneously be utilized to cool said power tube and heat said electrode arrangement.

2. The apparatus as defined in claim 1 wherein said power tube is provided with an external anode arranged to be cooled by air.

3. The apparatus as defined in claim 1 wherein the electrode terminals of said power tube are constituted by coaxially disposed cylindrical ring elements which engage contacts connected to said electrode arrangement.

4. The apparatus as defined in claim 3 wherein the electrode terminals of said power tube are arranged to be coaxial with the outline of the area enclosed by the electrode arrangement between the end plates.

5. The apparatus as defined in claim 4 wherein both of said side plates are provided with openings in the center thereof, and wherein said power tube extends beyond the outer surface of each of said end plates.

6. The apparatus as defined in claim 4 wherein the diameters of the individual cylindrical rings elements constituting the electrode terminals of said power tube successively increase in the axial direction, whereby the power tube may be easily inserted or removed. 7. The apparatus as defined in claim 4 wherein at least some of said terminal electrodes of said power tube are connected in said frequency generator via contact leads which extend into said ventilation channel via feedthrough terminals which act as inductances in said highfrequency generator.

8. The apparatus as defined in claim 4 wherein each of said end plates of said electrode arrangement comprises a capacitor plate of a respective capacitor for coupling one of said end plates and the rod-shaped electrodes connected thereto to the support for said electrode arrangement, and for coupling the other of said end plates and the rod-shaped electrodes connected thereto to a stationary plate juxtaposed the respective one of said end plates and connected to one said terminal electrodes. 5

k l 1 k l 

1. An apparatus for high-frequency drying of strip or thread shaped fibrous materials in a continuous process including, in combination: an electrode arrangement having the outline of a cylinder, means for mounting said electrode arrangement for rotation about the axis of said cylinder, said cylinder having a pair of end plates and plurality of rod-shaped electrodes connected to said end plates and disposed in the peripheral surface of said cylinder, said rod shaped electrodes extending in the axial direction of said cylinder and being arranged so that electrodes of opposite polarity are adjacent one another about the periphery of said cylinder, at least one of said end plates of said electrode arrangement being provided with an opening substantially in the center thereof which constitutes the intake of a forced air ventilation channel which includes the space between said end plates and whose outlet passes through the outer surface of said cylinder in all areas between adjacent ones of said electrodes, a power tube of a high-frequency generator which feeds power to said apparatus to produce the high frequency field between adjacent ones of said electrodes, said power tube being disposed in the intake of said ventilation channel and at least partially in the portion thereof disPosed between said end plates, whereby the air flowing through said ventilation channel can simultaneously be utilized to cool said power tube and heat said electrode arrangement.
 2. The apparatus as defined in claim 1 wherein said power tube is provided with an external anode arranged to be cooled by air.
 3. The apparatus as defined in claim 1 wherein the electrode terminals of said power tube are constituted by coaxially disposed cylindrical ring elements which engage contacts connected to said electrode arrangement.
 4. The apparatus as defined in claim 3 wherein the electrode terminals of said power tube are arranged to be coaxial with the outline of the area enclosed by the electrode arrangement between the end plates.
 5. The apparatus as defined in claim 4 wherein both of said side plates are provided with openings in the center thereof, and wherein said power tube extends beyond the outer surface of each of said end plates.
 6. The apparatus as defined in claim 4 wherein the diameters of the individual cylindrical rings elements constituting the electrode terminals of said power tube successively increase in the axial direction, whereby the power tube may be easily inserted or removed.
 7. The apparatus as defined in claim 4 wherein at least some of said terminal electrodes of said power tube are connected in said frequency generator via contact leads which extend into said ventilation channel via feedthrough terminals which act as inductances in said high-frequency generator.
 8. The apparatus as defined in claim 4 wherein each of said end plates of said electrode arrangement comprises a capacitor plate of a respective capacitor for coupling one of said end plates and the rod-shaped electrodes connected thereto to the support for said electrode arrangement, and for coupling the other of said end plates and the rod-shaped electrodes connected thereto to a stationary plate juxtaposed the respective one of said end plates and connected to one said terminal electrodes. 